All United States patents and application Publications referred to herein are hereby incorporated by reference in their entireties. In the case of conflict, the present specification, including definitions, will control.
In the fenestration industry, it is a common practice to temper glass lites for increased strength or safety. It is also common practice to coat glass lites with sputtered, infrared (IR) reflecting or low emissivity coatings. When both operations are required for a fenestration product, it is most economical to coat untempered glass with the IR reflecting layers first then temper in a subsequent operation.
In this manufacturing sequence, the sputtered IR reflecting stack must withstand the tempering temperatures reaching approximately 700° centigrade. Most sputtered coatings suffer two forms of degradation from this heat exposure. One form of degradation consists of the formation of optical haze or light scattering due to roughening or delamination of the IR reflecting layers.
A second form of damage is loss of mechanical durability. Between the manufacturing steps of tempering a coated lite and assembly into an insulating glass unit, a washing step is typically necessary. In this step, the coating is subjected to water and mechanical brushing. Often, coatings that have undergone heat treatment are more susceptible to removal of top layers or scratching damage during the washing step than coatings that have not undergone heat treatment.
Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, monolithic windows, and/or the like. In certain example instances, designers of coated articles often strive for a combination of high visible transmission, low emissivity (or low emittance, or “low-e”), and/or low sheet resistance (Rs).
Typical solar control coatings have a layer stack that includes glass/single dielectric layer (e.g. silicon nitride)/single nucleation layer (e.g. zinc oxide)/IR reflecting layer (e.g. silver) with subsequent dielectric layers and possibly subsequent silver layers.
Unfortunately, while such layer stacks may provide efficient solar control and satisfy other desired performance characteristics, such coatings may often times be lacking in terms of: (a) corrosion resistance to acid (e.g. HCl) and/or hot and humid conditions; (b) mechanical performance such as scratch resistance; and/or (c) thermal stability upon heat treatment for tempering, heat bending, or the like (i.e., ΔE* value(s)).
Accordingly, there exists a need in the art for coated articles that have improved characteristics with respect to (a), (b) and/or (c) compared to a conventional layer stack, but which still are capable of acceptable solar control (e.g., appropriate values of visible transmission and of solar heat gain coefficient (SHGC)), and for methods of making such articles.